This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Fisher is utilizing photoaffinity labeling, mechanical measurements, and, in collaboration with our lab, mass spectrometry to elucidate the structure and function of the outer hair cell motor protein, prestin. Because the azide-modified ligand that he is working with appears to bind to prestin with remarkable efficiency, it is likely that he will be able to identify covalently modified residues by using mass spectrometric and data analysis techniques that my lab has developed. This will permit him to investigate prestin's putative binding site for small carboxylic acids.